Genetic Studies of Campylobacter rectus Campylobacter rectus in an anaerobic Gram negative, motile rod which is often isolated from adult periodontitis lesions including periodontitis lesions found in patients with systemic diseases such as diabetes mellitus and Acquired Immunodeficiency Syndrome. While cross-sectional studies implicate this species as an important periodontal pathogen, relatively little is know about C. rectus. Identification of virulence factors would be an important step in elucidating the role this organism plays in the pathogenesis of periodontal disease. One potential virulence factor from C. rectus is a toxin which kills human polymorphonuclear leukocytes and promyelocytic HL-60 cells and which may allow C. rectus to overcome host defenses and to colonize the periodontium. The long term objective of these studies is to gain a better understanding of the role of C. rectus in human periodontal disease and in extraoral infections and then to develop strategies for the control and prevention of C. rectus associated periodontitis. Specifically we propose to; (1) examine genetic and serologic heterogeneity within C. rectus, (2) clone the toxin gene into E. Coli; (3) determine the structure and transcriptional organization of the gene or genes responsible for the toxin production, and; (4) study the structure/function relationships of the toxin gene product. Key Words: Campylobacter rectus, toxin, cloning